THIRTY-SEVENTH ANNUAL CONVENTION. 237 



that it will scratch. Strike a long arc with the two nails. Now 

 take a fine wire, tie a pencil or piece of chalk to one end and 

 measure it the exact length of the inside radius of the silo. Se- 

 lect any point on the inside curve, mark it with chalk, then 

 strike a point on this same curve as far as the string will reach 

 from the point selected. This will mark off a part of the circle 

 equal to 1-6 of the circumference of the silo. The enclosed 

 segment of the circle so described may be divided exactly in half 

 by laying a straight board from the two points designated, meas- 

 uring exactly half the distance and projecting the line from the 

 center of the circle through the middle point of the board de- 

 scribed. From these two points measure back toward the cen- 

 ter four inches inside the first circle and eight inches beyond the 

 outer circle. Now take a plank ten feet by eight inches and one 

 inch thick, saw exactly in the middle. Nail lightly to the floor 

 and with the scratching nails, scratch out the curves. This will 

 make one pattern each for the inner and outer forms. Since the 

 patterns are only half large enough for a full section, two of 

 them must be nailed together in order to make the full length. 

 The strips to be used in holding the two parts of the section to- 

 gether should be at least four feet long and cut on the same 

 circle as the form. 



The forms should be at least three feet high so that it will 

 take six pieces from the pattern to build each section of the 

 form. This will mean thirty-six of the inner and thirty-six of 

 the outer patterns. When cleated together three will be used 

 to make each section. In order to make the skeleton of the form 

 a strip of heavy wood at least one inch thick and two inches 

 wide and three feet long should be mortised into the three pat- 

 terns every fifteen inches apart. The outer stick on each end of 

 each form should be of 2x4 material. Cover each section with 

 a heavy strip of sheet iron or with matched lumber running up 

 and down. Any other bracing may be put between the patterns 

 that is found necessary. The patterns are all sawed in the 

 radial line leading to the center so that they will fit in a circle. 



